1. The Gloomy Prospect is a term originally by Plomin and Daniels (1987). As Turkheimer (2000) notes:

Plomin and Daniels (1987) almost identified the answer to this question, but dismissed it as too pessimistic:

"One gloomy prospect is that the salient environment might be unsystematic, idiosyncratic, or serendipitous events such as accidents, illnesses, or other traumas . . . Such capricious events, however, are likely to prove a dead end for research. More interesting heuristically are possible systematic sources of differences between families. (p. 8)"

The gloomy prospect is true. Nonshared environmental variability predominates not because of the systematic effects of environmental events that are not shared among siblings, but rather because of the unsystematic effects of all environmental events…
-- But indeed, it is Turkheimer's paper that has made the term famous.

2. The Gloomy Prospect is predominately about the unsystematic 'nonshared environment', rather than about missing heritability. In the section you quote, he extends this notion to include unknown genetic factors, but it's not the "classic" use ;)

2 comments:

ben_g
said...

Steve, how optimistic or pessimistic are you that there will be low hanging fruit with which to increase intelligence once we know which genes are involved? For example, that certain diets or low-side effect drugs will be available to rise your IQ a significant amount?

I'm totally unequipped to speak on it, but when I looked up the recently IQ-associated gene (http://www.genecards.org/cgi-bin/carddisp.pl?gene=FNBP1L) the related "drugs and compounds" includes Phosphatidylserine, which naturally occurs in food and has been found to possibly help with ADHD. Gave me hope that there may be some low hanging fruit?